Book/Report

FZJ-2019-00612

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Untersuchung der Eigenschaften des 9%-Chromstahles vom Typ 9Cr-0.5Mo-1.8W-V-Nb im Hinblick auf seine Verwendung als Rohrleitungsstahl und Kesselbaustahl unter erhöhten Temperaturen

Wachter, O. (Corresponding author)FZJ* ; Ennis, P. J.FZJ* ; Czyrska-Filemonowicz, A. ; Zielinska-Lipiec, A. ; Nickel, H.FZJ*

1995
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/21346

Report No.: Juel-3074

Abstract: In an extensive testing programme, the microstructure, tensile and impact properties, creep behaviour and the stress rupture strength of two heats of the tungsten-containing 9% chromium steel NF616 have been investigated. The creep rapture properties of weldments, one with a matching filler and another with a filler of composition similar to that of the steel E 9 1 1, and of weld simulations of the softened heat affected zone were determined and compared with those of the basis steel. The toughness of the weld metal and the HAZ of weldments was also investigated. The tendency for embrittlement of the coarse grained HAZ was assessed using weld simulation specimens. Alongside the size and distribution of precipitates (M$_{23}$ C$_{6}$, MX and Laves phase), the dislocation density was found to be the most significant structural parameter with respect to the long term strength properties. Tempering at temperatures just above the A$_{C}$, temperature, even for only a few seconds as used in the softened HAZ weld simulation, led to a considerable decrease in the creep resistance compared with the normal heat treatment, which explains the susceptibility of weldments to type IV cracking in weep tests. The creep behaviour depended on the applied stress, a Norton stress exponent of 16 being found for the high stress region and 6 for the low stress region. This observation must be taken into account in the extrapolation of data to long times; an overemphasis on test data obtained at high stresses can lead to an overestimation of the stress rupture strength. Although the weld metal of the matching filler weldment was found to be relatively brittle at room temperature, the coarse grained HAZ impact strength was high. A post weld heat treatment did not lead to embrittlement. The steel investigated may be used as boiler tubes and steam pipes operating at temperatures up to 620 $^{\circ}$C. The results of continuing creep rupture tests should be awaited before a general approval of the steel can be given.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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